Submarine Groundwater Discharge Along the Western Antarctic Peninsula: Relative Contributions of Recirculated Seawater and Subsurface Glacial Freshwater

Submarine groundwater discharge (SGD) is present along coasts worldwide but its effects on coastal ecosystems in polar environments are poorly understood. An initial survey of radium (^223,224Ra) and radon (²²²Rn), including twenty-six nearshore stations and two land-based stations, near Anvers Island on the Western Antarctic Peninsula (WAP) was completed during the 2012-2013 austral summer. Based on this initial survey, five shore-normal transects were selected and sampled weekly or bi-weekly over six weeks to capture geochemical changes and quantify groundwater/meltwater discharge over time. SGD was quantified at these five coastal sites using ²²³Ra and ²²⁴Ra activities measured in groundwater and surface water. Average ²²³Ra and ²²⁴Ra activities were elevated in porewaters and glacial meltwaters and decreased in surface water with distance from shore. Based on short-lived radium isotope end-member activities and using a mass balance model, SGD was on the order of 200 m³ d^-1 per m of shoreline. The high discharge rates and H and O isotopes from water samples indicate that meltwater may be a large portion of SGD during summer months with warmer temperatures and demonstrates the need for further SGD investigations to quantify flow and nutrient contributions in nearshore environments. Primary production in iron-limited waters offshore of the WAP is believed to be fueled by continentally-derived sediments, and SGD could potentially be an important and yet unmeasured source of iron to continental shelf waters in this location.